The use of microscopes in the performance of tasks relating to magnifying small objects is common in many areas of science, medicine and manufacturing. Stereomicroscopes, in which the user sees left-eye and right-eye views and forms a three-dimensional or stereoscopic view, are also very common. That is, a stereoscopic view provides the normal stereoscopic sense of depth (“stereopsis”) enjoyed by the natural eyesight of a human user having two eyes, (e.g. normal eyesight). Stereomicroscopes are typically used in scientific research, education, surgery, medical and dental examinations, and industrial inspection and manufacturing where depth perception or a depth of field of the view is desirable.
Typically a user sits in an upright position with hands in front at about waist height for object manipulation. Eyepieces are generally located such that the user peers down at an angle into them to see the magnified image of the object. Such a position is generally accepted as ergonomic, intended to maximize productivity by reducing user fatigue and discomfort. In fact in some jobs the worker is in this position for hours each workday. However the use of eyepieces in optical systems is often problematic, particularly in microscopy. Eyepieces require the user to maintain a fixed position while observing the object or desired field of view, such that frequent or prolonged use can lead to eye, neck, and/or back strain. In addition, visualization can be difficult due to misalignment between eyes and eyepieces, or between eyeglasses and eyepieces, and a significant amount of time is needed to adjust, focus, and clean the eyepieces.
Furthermore, only one user or observer at a time can view images generated by the microscope and the user can no longer see what is happening in the surrounding environment. In addition, microscopes, as such, cannot store images or sequences of images for later reference, process them in special ways, or transmit them to remote viewing sites. Therefore, it is often desirable to use electronic imaging to replace the eyepiece optics of a microscope.
As noted above, eyepieces require the user to maintain a fixed position while observing the object or desired field of view, such that frequent or prolonged use can lead to eye, neck, and/or back strain. In addition, visualization can be difficult due to misalignment between eyes and eyepieces, or between eyeglasses and eyepieces, and a significant amount of time is needed to adjust, focus, and clean the eyepieces. Frequently, the user using the eyepieces can no longer see what is happening in a surrounding environment.
As is well known in the art, the use of two electronic cameras mounted on a stereomicroscope, each with a slightly different point-of-view provided by the microscope's optics can replicate the natural stereoscopic view perceived by human eyes through the microscope. In particular, when the images from the two cameras are displayed on a suitable display device, a stereoscopic, or three-dimensional, or “3D”, image is generated.
In the current art, two independent cameras are typically attached to the stereomicroscope. The optical path to each camera is made by a beam-splitting element that sends some portion of light from each of the two optical paths of the microscope, in the portion of the path between the objective lens or lenses and eyepiece lenses, through the appropriate camera's lens system, to the camera's focal plane while the rest of the light continues on to the eyepieces. These cameras can be still-image capture cameras or moving-image capture cameras.
In the case of video cameras, signals from the two cameras are transmitted through two or more cables to camera control units (CCU), computers, recorders, or display devices. The image sensors within the cameras are usually of a technology known in the art as charge-coupled device (CCD). A filter to reduce the amount of infrared light reaching the sensor is usually integrated into the sensor assembly and is not removable.
In the current art, the moving-image cameras are typically standard definition (SD) video cameras, that is, cameras that conform to the NTSC or PAL video standards. Unfortunately, the resolution of such standard definition video cameras has generally not been adequate to replace the eyepieces entirely. The NTSC and PAL systems suffer from low resolution, poor color fidelity, and motion artifacts (due to the interlaced nature of the raster scan). Imagery from these cameras is not suitable for those applications, such as surgery, precision assembly, and scientific research, which require the highest quality visualization.
Because such systems still generally have the eyepieces, or provisions for them, the electronic display cannot be located at the optimally ergonomic position, (e.g. where the eyepieces are located). So the display is generally located off to one side or above the eyepiece line-of-sight. This has the effect that using the electronic display alone solves some of the eyepiece problems but creates new problems.
The two camera systems described above have further disadvantages. Obtaining and maintaining stereoscopic alignment (necessary for comfortable, long-term viewing) can be difficult when two independent cameras are mounted on a microscope, each with their own adapters. The cameras generally protrude from the general body of the microscope and are often mounted in a way that is fragile and prone to breakage. Protruding cameras can interfere with existing microscope knobs and controls and other apparatuses in the workspace, limiting possible installation configurations, and their size or position can block the user's view. Dual camera systems generally require numerous mounting parts, resulting in less reliability and more cost than a single, integrated camera module.
In addition, there are also problems with mounting and connecting the cameras to displays or storage media. The use of two cameras requires multiple cables and connectors, resulting in less reliability and more difficult installation than a single cable/connector arrangement of the present invention. The two camera system also typically requires two CCUs and two storage devices and requires that they be synchronized for best image quality. Such synchronization significantly increases the complexity of the design, capital cost and maintenance of the system.
Such cameras do not allow precise positioning of the imaging sensors to each other for best stereopsis and comfortable viewing, particularly when two off-the-shelf cameras are used. The cameras must be individually focused after mounting, and, should adjustments such as brightness and contrast be needed, each camera must be controlled individually. Where the cameras contain irises, they must also be individually adjusted for each camera, resulting in the potential for unequal amounts of light entering each camera, which can lead to difficult 3D viewing and eyestrain. All these factors demonstrate that the installation and maintenance of such a system can be time-consuming and require a skilled technician.
Image processing is also problematic in such present art systems. As noted above, the cameras must be electronically linked in some way so that the two image streams are synchronized, creating additional cost, vulnerability and complexity. The images that result from the two cameras are generally taken directly to the stereoscopic display device. Should the user require image processing, storage, transmission, or display on alternative displays, additional processing units are required for each data stream, creating yet more additional cost, vulnerability and complexity.
Information relevant to attempts to address these problems can be found in U.S. Pat. No. 5,867,210 and U.S. Patent Application No. 2005/0111088, and at http://www.stereoimaging.com/products/dentimag.html, and http://www.leica-microsystems.com/eebsite/products.nsf/allids/ECFFFC6CF17470FEC1257C6D002FBF 06 (See Digital Photo/Leica IC 3D). However, each one of these attempted solutions suffer from one or more of the following disadvantages: (i) the device creates two independent output signals, (ii) the device is not lightweight or compact, (iii) the device does not provide sufficient image processing, recording, or transmission capability, (iv) the device does not have adequate resolution in real-time for many applications, (v) the device was designed to be used with eyepieces, or (vi) the device is limited with respect to the make or type of optical instruments with it which can be used.